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Taiwan Semiconductor Corporation SMAJ28H
- Part No.:
- SMAJ28H
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ28H.pdf
- Description:
- TVS DIODE 28VWM 50VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:4,415
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Product details
Overview
SMAJ28H from Taiwan Semiconductor is a unidirectional 400W surface-mount transient voltage suppressor (TVS) diode in DO-214AC (SMA) package, with 28V working stand-off voltage (VWM), 31.1–38.0V breakdown voltage (VBR) at 1mA test current, and 50.0V maximum clamping voltage (VC) at 8.0A peak impulse current. It delivers fast response (<1.0ps), low leakage (<1µA above 28V), and AEC-Q101 qualification for automotive-grade surge protection in DC/DC converters and power supplies.
For engineers reviewing the SMAJ28H datasheet, SMAJ28H pinout, SMAJ28H application, or SMAJ28H equivalent, this page provides verified electrical parameters, clamping performance under 10/1000µs waveform, ISO 7637-2 compliance details, thermal limits (TJ = –55°C to +150°C), and direct alternative part comparisons - all specific to SMAJ28H and validated against Taiwan Semiconductor's A2102 specification sheet.
Technical Context
The SMAJ28H operates as a unidirectional avalanche diode, designed to clamp transient overvoltages by entering breakdown when reverse voltage exceeds its VBR range (31.1–38.0V). Its glass-passivated junction ensures stable leakage (<1µA at VWM = 28V) and robust ESD/EMI immunity.
It sustains 400W peak pulse power per 10/1000µs waveform up to TA = 25°C, derating linearly above that ambient temperature, and supports steady-state power dissipation of 1W. The device meets ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b requirements for automotive electronics, with moisture sensitivity level (MSL) 1 per J-STD-020.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 28 V - Maximum continuous reverse operating voltage before clamping begins |
| VBR min/max | 31.1 V / 38.0 V at IT = 1 mA - Confirmed breakdown threshold range for reliable turn-on margin |
| VC @ IPPM | 50.0 V at IPPM = 8.0 A - Clamped voltage during 10/1000µs surge, limiting downstream stress |
| PPPM | 400 W (10/1000µs) - Peak surge energy handling capacity without failure |
| IR @ VWM | <1 µA - Negligible leakage current at rated stand-off, minimizing standby power loss |
| TJ max | +150 °C - Maximum junction temperature enabling operation in under-hood automotive environments |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline with 0.060g mass and J-STD-002 solderability |
Pinout & Package
DO-214AC (SMA) package: molded plastic case with cathode band marking; matte tin-plated leads; polarity indicated by cathode band on body; weight ≈ 0.060 g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to system ground or lower-potential rail in unidirectional TVS configuration |
| Cathode | Reverse-biased clamping terminal | Connected to protected line (e.g., 28V rail); conducts avalanche current during overvoltage events |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive applications including engine control units and ADAS power rails |
| Clamping voltage ≤50.0V at 8.0A | Ensures protected ICs (e.g., 3.3V/5V logic, CAN transceivers) remain below absolute maximum ratings during surge |
| Response time <1.0ps | Fast enough to suppress ESD and fast transients before sensitive circuitry responds |
| ISO 7637-2 compliant (Pulse 1/2a/2b/3a/3b) | Meets full suite of automotive load-dump and supply interruption immunity requirements |
| Moisture sensitivity level 1 | Enables standard SMT reflow without baking or special handling |
Applications
| Automotive Power Rail Protection | Industrial DC/DC Converter Input |
|---|---|
Use Scenario: Protecting 24V battery-fed ECUs from load dump and alternator transients in passenger vehicles. IC Role / Device Role / Timing Role: Unidirectional TVS placed between 24V rail and chassis ground to clamp surges up to ±100V. Use Value: SMAJ28H's 50.0V clamping at 8.0A ensures microcontrollers and CAN PHYs stay within safe operating area during ISO 7637-2 Pulse 5a events. | Use Scenario: Safeguarding isolated 28V-to-5V buck converter inputs in factory automation controllers. IC Role / Device Role / Timing Role: Primary overvoltage clamp on secondary-side 28V bus prior to regulator input. Use Value: With VWM = 28V and TJ max = +150°C, SMAJ28H remains inactive during normal operation yet triggers reliably during 400W surges. |
| LED Driver Supply Line | Telecom Power Interface |
Use Scenario: Suppressing switching noise and lightning-induced spikes on constant-current LED driver inputs. IC Role / Device Role / Timing Role: Standoff-rated TVS on 28V input stage to prevent MOSFET gate oxide damage. Use Value: Sub-1µA leakage at 28V avoids efficiency loss, while 31.1–38.0V VBR guarantees consistent activation across temperature. | Use Scenario: Front-end surge protection for 28V PoE-powered remote radio units. IC Role / Device Role / Timing Role: First-line defense against induced surges on outdoor-facing DC power entry points. Use Value: DO-214AC package enables high-density layout; MSL 1 rating supports automated assembly without pre-bake delays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar transient suppression applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Littelfuse SMAJ28A | Lower VBR range (31.1–34.4V); tighter tolerance; same DO-214AC package and 400W rating | Preferred where tighter clamping consistency is required across production lots | Select SMAJ28A if design requires reduced VBR variance; SMAJ28H offers broader VBR spread for cost-sensitive volume production |
| ON Semiconductor SMAJ28 | Identical VWM (28V), VBR (31.1–38.0V), VC (50.0V), and package; RoHS/halogen-free compliant but not AEC-Q101 qualified | Suitable for industrial/commercial use where automotive qualification is not mandated | Choose SMAJ28H for automotive systems requiring AEC-Q101; use ON Semi SMAJ28 where qualification overhead is unnecessary |
Compared with Littelfuse SMAJ28A and ON Semi SMAJ28, SMAJ28H uniquely combines AEC-Q101 qualification, ISO 7637-2 compliance, and MSL 1 handling - making it the only option among the three certified for under-hood automotive deployment without additional reliability validation.
Availability
SMAJ28H is available at Aetrix Electronics and suitable for automotive power rail protection, industrial DC/DC converter input stages, and LED driver supply lines requiring stable component supply and full AEC-Q101 traceability.
Supply support for SMAJ28H includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Taiwan Semiconductor Corporation (TSC) is a vertically integrated semiconductor manufacturer specializing in discrete power devices, TVS diodes, rectifiers, and MOSFETs, with global distribution and AEC-Q101-compliant production lines.
The SMAJ series was developed specifically for automotive and industrial transient suppression, emphasizing high peak power density, low clamping voltage, and robust process-controlled junction passivation in surface-mount packages.
FAQ
What is the maximum clamping voltage of SMAJ28H under a 10/1000µs surge?
The SMAJ28H has a maximum clamping voltage (VC) of 50.0 V when subjected to an 8.0 A peak impulse current with a 10/1000µs waveform, as specified in Taiwan Semiconductor's A2102 datasheet. This value ensures protected downstream components remain within safe voltage limits during standardized surge events. The clamping performance is guaranteed across the full operating temperature range and is integral to SMAJ28H's compliance with ISO 7637-2 Pulse 5a testing.
Is SMAJ28H suitable for bidirectional transient suppression?
No, SMAJ28H is a unidirectional TVS diode, indicated by the absence of "CAH" or "CH" suffix and confirmed by its single cathode band marking and electrical specifications applying only in reverse bias. For bidirectional protection at 28V standoff, Taiwan Semiconductor specifies SMAJ28CH - a distinct part with symmetrical breakdown in both directions. Using SMAJ28H in bidirectional configurations risks failure during positive-going transients.
Does SMAJ28H meet automotive qualification standards?
Yes, SMAJ28H is explicitly AEC-Q101 qualified and meets ISO 7637-2 Pulse 1, 2a, 2b, 3a, and 3b requirements for automotive electronics. Its construction includes glass-passivated junctions, MSL 1 moisture resistance, and JESD201 Class 2 whisker resistance - all verified per AEC-Q101 stress test conditions. This makes SMAJ28H appropriate for engine control modules, body control units, and ADAS power domains.
What is the thermal derating behavior of SMAJ28H above 25°C ambient?
SMAJ28H's peak pulse power (400W) is derated linearly above TA = 25°C, following the curve in Figure 2 of the A2102 datasheet. At 85°C ambient, its PPPM drops to approximately 240W; at 125°C, it falls to ~120W. This derating must be applied in thermal simulations for under-hood applications. Steady-state power dissipation remains limited to 1W regardless of ambient, governed by package thermal resistance.
How does SMAJ28H differ from SMAJ28AH?
SMAJ28AH features a tighter breakdown voltage range (31.1–34.4V vs. 31.1–38.0V for SMAJ28H), achieved via enhanced process control. Both share identical VWM (28V), VC (45.4V for SMAJ28AH vs. 50.0V for SMAJ28H), and package (DO-214AC). SMAJ28AH's lower clamping voltage improves protection margin for ultra-sensitive loads, while SMAJ28H offers broader VBR tolerance for cost-driven designs where slight variation is acceptable.
SMAJ28H Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AC, SMA
- Series:
- SMAJ
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 28V
- Voltage - Breakdown (Min):
- 31.1V
- Voltage - Clamping (Max) @ Ipp:
- 50V
- Current - Peak Pulse (10/1000µs):
- 8A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- -
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ28H FAQ
1.How can I place an order for SMAJ28H through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ28H on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SMAJ28H reliable?
The price and inventory of SMAJ28H are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ28H is usually 5 days.
3.What payment methods are accepted for SMAJ28H?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ28H transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ28H?
SMAJ28H orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ28H order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SMAJ28H?
For technical support, including SMAJ28H datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ28H requirements.
6.How does Aetrix verify that SMAJ28H is sourced from the original manufacturer or authorized distributors?
All SMAJ28H products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SMAJ28H meets industry standards.
7.What is the process for return or replacement of SMAJ28H?
All SMAJ28H units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ28H, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SMAJ28H part is unused and in its original packaging.
Return procedure for SMAJ28H:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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